Cos'è crust? Cos'è crust? The hard outer portion or surface area of bread.A piece of bread consisting mostly of the hard outer portion.A piece of bread that has become hard and dry. A pastry shell, as of a pie or tart.A hard crisp covering or surface: snow with a firm crust. A hard deposit formed on the interior of a wine bottle as the wine matures.Geology The exterior portion of the earth that lies above the Mohorovičić discontinuity.Geology The outermost solid layer of a planet or moon.The hard outer covering or integument of certain plants and animals, such as lichens and crustaceans.Pathology An outer layer or coating formed by the drying of a bodily exudate such as pus or blood; a scab.Informal Insolence; audacity; gall.To cover with a crust.To form into a crust.To become covered with a crust.To harden into a crust.